Shrinkage, hydration, and strength development of limestone calcined clay cement (LC3) with different sulfation levels

This study investigated autogenous shrinkage of limestone calcined clay cement (LC3)-based mixes with various
sulfation levels of hemihydrate. Physicochemical evolution and strength development were also monitored.
Superior mechanical performance of the mixes was achieved at an optimal sulfation level, although the shrinkage
was reduced with the sulfate content. Calorimetry data showed the hemihydrate delayed and broadened the
second aluminate peak. Both gypsum and ettringite formed early during hydration, and carboaluminates were
observed after 3 days of curing. Ettringite in the LC3 mixes was of smaller sizes in comparison to that in the
ordinary Portland cement (OPC) mixes, attributable to the pore refinement in the LC3 matrices. The content of
portlandite (Ca(OH)2) was reduced with the curing time due to pozzolanic reactions. The findings demonstrated
a coupling effect of both the chemical and microstructural change on the observed autogenous shrinkage and the
consequent performance of LC3-based concrete composites.